Paul Anthony Ciancia, 23, is pictured in this undated handout photo courtesy of the FBI. A lone gunman stormed into a packed terminal at the Los Angeles International Airport and opened fire with an assault weapon on November 1, 2013, killing a federal security agent before he was shot and captured, authorities said. Special Agent David Bowdich of the FBI identified the suspect as Ciancia, a resident of the Los Angeles area, who was being treated for his injuries at a local hospital. [Photo/Agencies]

LOS ANGELES - The gunman charged in the deadly shooting at Los Angeles International Airport lay bloodied and handcuffed on the floor of Terminal 3 after being gunned down by police, but he replied to critical questions that helped authorities lock down the scene.

Paul Ciancia, 23, was hauled away moments later on a stretcher and later heavily sedated for medical reasons, but not before he told investigators he had acted alone when he opened fire in the terminal, a law enforcement official who has been briefed on the investigation said on Sunday.

Ciancia, an unemployed motorcycle mechanic who recently moved to Los Angeles from the small, working-class town of Pennsville, New Jersey, also told police a friend had dropped him off at LAX on Friday just moments before he shot a Transportation Security Administration officer at point-blank range and wounded three other people, including two more TSA workers.

Officials do not believe that the friend knew of the shooter's plans. Ciancia arrived at the airport in a black Hyundai and was not a ticketed passenger.

Ciancia was under 24-hour armed guard at the hospital Sunday after being shot four times, the official said. He was sedated for medical reasons, the official said, adding that one gunshot to the mouth blew a molar out of his jaw.

Ciancia is facing charges of murder of a federal officer and committing violence at an international airport. The charges could qualify him for the death penalty.

It was not immediately clear when he would make a first court appearance given his medical condition.

In court documents and interviews, authorities spelled out a chilling chain of events, saying Ciancia walked into the airport, pulled a .223-caliber assault rifle from his duffel bag and fired repeatedly at point-blank range at 39-year-old TSA officer Gerardo I. Hernandez, killing him.

He then fired on at least two other uniformed TSA employees and an airline passenger, who all were wounded, before airport police shot him as panicked passengers cowered in stores and restaurants, authorities said.

It wasn't clear why Ciancia targeted TSA officers, but what he left behind made it clear he intended to kill any of them that crossed his path, authorities revealed.

The shooter's duffel bag contained a handwritten letter signed by Ciancia stating he'd "made the conscious decision to try to kill" multiple TSA employees and that he wanted to "instill fear in their traitorous minds", FBI Agent in Charge David L. Bowdich said.

"Black, white, yellow, brown, I don't discriminate," the note read, according to a paraphrase by a law enforcement official briefed on the investigation. The official spoke on the condition of anonymity because he was not authorized to speak publicly.

The screed also mentioned "fiat currency" and "NWO", possible references to the New World Order, a conspiracy theory that foresees a totalitarian one-world government.

The letter also talked about "how easy it is to get a gun into the airport," the law enforcement official said.